Among prior art compounds which inhibit a Na.sup.+ /Ca.sup.2+ exchange system selectively and prevent overload of Ca.sup.2+ in cells regarded as important in the cell injury mechanism after ischemia or reperfusion, there are known compounds as described in Japanese Patent Kokai 7-41465 and WO97/09306. However, there have not been known any compounds with a phenoxyaniline skeleton which have an inhibitory action on a Na.sup.+ /Ca.sup.2+ exchange system.